- 1 November 2015 -
Throughout the geologic ages, the Earth has been a treasure-bearing chest, hiding all its riches way beneath its surface, literally. In 1530, a striking discovery was made unraveling one of the most distinctive treasures of the Earth that brought colour to the world of geology – fluorite (Gem Select, 2006). Fluorite is widely used to manufacture Teflon, hydrofluoric acid, glow-in-the-dark materials, steel, optical lenses, and ornamental figurines, making it diversified in many forms in today’s industry.
Fluorite is part of the halide family of minerals due to its derivation from its geologic form – calcium fluoride (CaF2). It is a very common mineral that typically crystallizes in an isometric cubic motif, as shown in Figure 1, but can also take on other formations (Akchurin, et al., 2006). Fluorite is an allochromatic mineral, meaning that it is tinted with elemental impurities, which is the direct cause for it to naturally occur in all colours of the spectrum. Consequently, it has been deemed “The Most Colourful Mineral in the World” as it displays every colour of the rainbow in various shades (Gemology Project, 2012).
Fluorite is a unique mineral not only due to its widely diverse occurrence around the world but also because it is one of the few minerals on the surface of Earth to possess the ability to fluoresce under ultra violet light. In 1852, a physicist named George Gabriel Stokes discovered the ability of specimens composed of fluorite to produce a blue glow when ultra violet light was shone, as shown in Figure 2, which he described as “beyond the violet end of the visible spectrum” (Okenga, 2011). Thus, the term “fluorescence” was born as Stokes named this phenomenon after the mineral, fluorite (Okenga, 2011). The name fluorescence gained a worldwide acceptance from various fields of science such as optical crystallography, molecular biology, and mineralogy.
Globally, fluorite deposits are mined in hydrothermal areas of the Earth and is commonly associated with igneous rocks where it occurs as a vein deposit, forming in various parts of a host rock (i.e. galena, quartz, dolostone, and calcite). One of the largest deposits of fluorite in North America is situated in the Burin Peninsula, Newfoundland, Canada (Adams, 2013).
There are several uses for fluorite in today’s industry, many of which include the different chemical forms and conversions of the mineral. When fluorite reacts with sulfuric acid, it liberates hydrogen fluoride, as illustrated in the chemical formula below, which is converted into different chemical commodities like fluorocarbons in aerosols and solvents.
In addition, fluorite has a low refractive index, which is a huge contributing factor for the optic lens industry due to the fact that lenses made from fluorite have low chromatic aberration (Bello, 2006). This simply means that they represent a large spectrum of light in one place. It is also able to display “fringes” of colour along boundaries that separate dark and bright parts of the image, because each colour in the optical spectrum cannot be focused at a single common point. This makes the material attractive for telescope and camera lens makers.
Thus, it is valid to infer that fluorite, being a naturally occurring mineral in the Earth’s surface, will be sustained in today’s industry as one of the most unique and diverse resources. This uncovered geologic treasure will truly continue to bring colour to ongoing fields of science.
References
Adams, T., 2013. Mineral commodities of Newfoundland and Labrador: Fluorite. St. John’s, NF: Government of Newfoundland and Labrador, Dept. of Mines and Energy.
Akchurin, M., Gaĭnutdinov, R., Smolyanskiĭ, P. and Fedorov, P., 2006. Anomalously high fracture toughness of polycrystalline optical fluorite from the suran deposit (South Urals). Dokl. Phys., 51(1), pp.10-12.
Bello, I., 2006. Book Review: Bulk Crystal Growth of Electronic, Optical and Optoelectronic Materials. By Peter Capper (Ed.). Adv. Mater., 18(13), pp.1775-1776.
Chemlegin, 2013. Fluorite. [online] Available at: <https://chemlegin.files.wordpress.com/2013/05/2013_05_24_fluorite_fluorescence.gif> [Accessed 30 Oct. 2015].
Gem Select, 2006. Fluorite Gemstone Information. [online] Available at: <http://www.gemselect.com/gem-info/fluorite/fluorite-info.php> [Accessed 27 Oct. 2015].
Gemology Project, 2012. Causes of color – The Gemology Project. [online] Available at: <http://gemologyproject.com/wiki/index.php?title=Causes_of_color> [Accessed 30 Oct. 2015].
Guillou-Gotkovsky, E., 2011. History of Fluorite. [online] Spathfluor. Available at: <http://www.spathfluor.com/_open/open_us/us_op_general/us_history-fluorite.htm> [Accessed 30 Oct. 2015].
Ockenga, W., 2011. An Introduction in Fluorescence. [online] Leica Science Lab. Available at: <http://www.leica-microsystems.com/science-lab/an-introduction-in-fluorescence/> [Accessed 30 Oct. 2015].